Apparently there is some sort of technique? If you believe anything Wikipedia says anyway…
“Some “screaming” vocalists have had problems with their throats, voices, vocal cords, and have even had major migraines from screaming when doing it incorrectly. Some vocalists of metalcore bands have had to stop screaming, or making music altogether, or even undergo surgery (such as Corey Taylor of Slipknot) due to screaming in harmful ways that damage the vocal cords.
Damage to the vocal cords can usually be avoided by using a screaming technique that incorporates the thoracic diaphragm. By using this technique, air is pushed out with the stomach, taking tension off of the throat.”
http://en.wikipedia.org/wiki/Screaming_%28music%29#Heavy_metal